Rising damp is one of all talked about topic because it is within every house .This How To guide takes you through identifying rising damp, the causes and how to effectively deal with it. A large part of this guide is given over to effectively identifying rising damp in your home, telling it apart from much more common damp issues. We also bust some myths around rising damp and its own treatment.
What is Rising Damp?
Rising damp is a relatively rare form of damp that impacts the walls of buildings. It occurs when moisture from the bottom travels up through the walls by capillary action. This means that ground water is effectively sucked up through tiny tubes in the bricks, like a group of straws. This water contains salts that also travel up through the wall.
Around the affected wall, you get other porous building materials such as plaste rwork and the timber within the ground boards, joists and skirtings. These materials will also absorb the ground water easily and you may find proof of wet rot in the timber.
Generally Rising damp is first noticed by the damage it causes to the inner walls of the building. Plaster and paint can deteriorate and any wallpaper will loosen. A obvious stain often appears on the wall as a tide mark at the point where in fact the ground water has reached. You may also see salts blooming on the internal surface. That is something often associated with rising damp and definitely will lead to the debonding of paints and even plaster work. Externally, mortar may crumble and white salt stains may appear on the walls. We will enter in the common signs of rising damp in greater detail later in the guide.
Causes of Rising Damp
Rising damp is a relatively rare form of damp that influences the walls of buildings. It occurs when moisture from the bottom travels up through the walls by capillary action. This means that ground water is effectively sucked up through tiny tubes in the bricks, such as a series of straws. This water contains salts that also travel up through the wall.
Around the damaged wall, you get other porous building materials such as plaster work and the timber found in the ground boards, joists and skirting. These materials will also absorb the ground water easily and you’ll find evidence of wet rot in the timber.
Sometime the DPC can remain intact, however the DPC can be bridged. That’s where the damp from the bottom will be able to travel up past the DPC due to a construction fault.
Examples of this include:
Debris in the wall cavity or sub floor void.
Internal or external renders / plasters overlapping the DPC
External ground levels being raised above the DPC.
Inappropriate insulation material in the cavity.
Solid floors
Intersecting masonry structures / abutting garden walls.
Rising Damp – Internal Walls
Most people first notice an issue with rising damp on internal walls. Rising damp often leads to tide marks on your internal walls up to the height where in fact the water has reached. In most cases, these tide mark stains appear up to and including metre above the skirting board. In certain very rare cases, water can travel beyond this aspect.
The height the water reaches will depend on several key factors. Included in these are the pore structure of the bricks and mortar and the pace of evaporation. Masonry containing a high proportion of fine pores will allow the to rise higher than one with less pores. Rising damp may appear up to 1.5 metres and even higher in a few very rare instances.
The water from the ground often contains salts that are then deposited on the wall when this evaporates. These salts can cause the paint to bubble and a white fluffy deposit to be left on the top. You will discover two main types of salt – sulphates which lead to crusty white patches and invisible hygroscopic salts known as nitrates and chlorides. The hygroscopic salts continue steadily to draw moisture and for that reason must be treated.
What causes rising damp in internal walls?
Rising damp in internal walls is caused by the same movement of ground water up through the brickwork by capillary action. It’s the result of a failed or non-existant DPC or when the DPC has been bridged.
Rising Damp External Walls
Rising damp can affect both internal and external walls. When looking for evidence of rising damp on external walls, again you should keep an eye out for tide marks. You may even see some of the mortar crumbling between your bricks or stonework and salt deposits too.
Signs of Rising Damp
Rising damp is a relatively rare form of damp and treatment is only going to work if it is correctly diagnosed. It is therefore vitally important to get a professional diagnosis from a knowledgeable surveyor – this calls for a rising damp survey of your home including analysis of the salts.
It can be hard to distinguish rising damp from other varieties of damp like condensation or penetrating damp.
Having said that, the following are some of a lot more common signs of rising damp that you can consider:
Tide marks of salts
Dark patches on walls that can be damp to touch – for a better indication of rising damp you want to determine that the brickwork / masonry is actually wet and not only the plaster or wallpaper.
Staining of wall coverings, peeling wallpaper & blistering paint.
Damp and musty smell.
Discolouration & fragmenting plaster.
Decaying timber e.g. skirting boards, floor boards, floor joist
Rising Damp Treatment
The cream is injected or hand-pumped into specially-positioned holes in the mortar course. Once inserted, the damp proofing cream reverts to a liquid. This allows it to penetrate the bricks and achieve complete absorption. Mainly because it cures, it creates a powerful water-repellent barrier and a new chemical DPC that stops water from rising in the wall. For full instructions about how to treat rising damp with damp proofing cream read our guide to injecting damp proof courses.
Alternatively, you can install a fresh damp proof membrane to do something as a damp proof course. This is a much bigger and more complicated process that involves taking out each brick along the failed mortar course and installing a fresh physical damp proof membrane.
Waterproof Lab EPDM Rubber Waterproofing
22 Plantation Road,Ottery, Cape Town, 7708
+27 78 012 5339
+27 21 415 1694
